head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Execution · Pure Mechanics
A classic 2D Mario platformer rewarding tight jump execution above all.

Execution · Pure Mechanics
Precise jump execution across fixed levels with secrets to memorise.
New Super Mario Bros. U Deluxe leans Execution (Pure Mechanics); Super Mario World leans Execution (Pure Mechanics).
New Super Mario Bros. U Deluxe leans a little harder on execution, though the gap is small.
New Super Mario Bros. U Deluxe
precise jump and platforming execution
Super Mario World
Perfect inputs trivialise every jump, spin and cape flight
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
New Super Mario Bros. U Deluxe
fixed enemy patterns, no adaptation
Super Mario World
Scripted Koopas adapt to nothing
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
New Super Mario Bros. U Deluxe
minor enemy placement randomness
Super Mario World
Levels are fixed; nothing hidden survives one playthrough
Super Mario World leans a little harder on optimization, though the gap is small.
New Super Mario Bros. U Deluxe
level routing for speed/collectibles
Super Mario World
Secret exits and route knowledge add a modest solvable layer
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.